The compound of formula (I) reported below, the chemical name of which is (β)-17-(pyridin-3-yl)androsta-5,16-dien-3-ol acetate, is commonly referred to by the name abiraterone acetate:

Abiraterone acetate is a steroid with pharmacological activity that is useful for slowing down the progression of prostate cancer at an advanced stage.
Carcinoma of the prostate is the principal tumor in the male population in Western countries, where it is also the second cause of cancer death.
Abiraterone acetate has proved capable of prolonging the life of these patients and of improving their quality of life, and is the first element of a new class of non-chemotherapeutic medicinal products with targeted action, that are capable of acting directly on the self-feeding process of the tumor.
Advanced prostate carcinoma cells are able to autonomously synthesise testosterone from cholesterol, single-handedly feeding its own growth and development thanks to the CYP17 enzyme, which is a key element of the synthesis of androgens and, in particular, of testosterone.
Abiraterone acetate is an efficient inhibitor of the CYP17 enzyme and is thus a medicinal product that is able to deeply inhibit the production of testosterone and other androgen hormones by acting at the level of the adrenal gland, the testis and, above all, of the tumor microenvironment.
Abiraterone acetate is described for the first time in international patent application WO 93/20097 A1. Example 1 of this application describes the preparation of abiraterone acetate (I) from prasterone acetate (III) according to the following scheme:
where the intermediate (II) is 3β-acetoxyandrost-5,16-dien-17-yl-trifluoromethanesulfonate. The intermediate (II) is obtained by reacting prasterone acetate (III) with trifluoromethanesulfonic anhydride (triflic anhydride) in methylene chloride in the presence of 2,6-di-t-butyl-4-methylpyridine as a base. The intermediate (II) recovered by flash chromatography on silica gel is reacted with diethyl-(3-pyridyl)borane in the presence of a palladium (II) catalyst to yield abiraterone acetate. The recovery of the product takes place by flash chromatography on silica gel as well.
An alternative synthesis is described in Organic Preparations and Procedures Int., 29 (1), 123-134 (1997). According to the authors this new preparation would overcome the problem of a large-scale production of abiraterone, not resolved by the afore-described syntheses. The synthesis scheme (set out below), actually, seems of doubtful industrial applicability, not so much on account of the fact that there are four reactions involved compared to the two reactions of the synthesis of WO 93/20097 A1, but because the reagent necessary for obtaining the “hydrazone” intermediate is hydrazine, a known carcinogenic product.

International patent application WO 2006/021777 A1 describes and claims an optimisation of the process of WO 93/20097 A1, based on the study of the reaction conditions. According to the inventors (WO 2006/021777 A1, p. 3), the described process keeps within acceptable levels the formation of the impurity of formula:
and eliminates the need for chromatographic purifications.
The key element of this new process is the choice of base to be employed in the reaction from prasterone acetate (III) to intermediate (II), which is selected from the tertiary or heterocyclic amines pyridine, 2,6-lutidine, N-methylmorpholine, trimethylamine, triethylamine, 1,4-diazabicyclo[2.2.2]octane (DABCO), N,N-diisopropylethylamine (DIPEA), 1,8-diazabicycloundec-7-ene (DBU) and 1-azabicyclo[2.2.2]octane (commonly known as quinuclidine). The formation of the intermediate (II) is obtained in this process with a yield of 60% (example “Triflate formation 3”, p. 14 of WO 2006/021777 A1); the reported yield is in fact 80% of a 3:1 mixture of intermediate (II) and starting prasterone acetate. The example “Salt formation” on p. 15 describes the formation of the methanesulfonate of abiraterone as a purification method of the latter from the unreacted portion of prasterone. In this case too, the proposed synthesis route does not appear to be of real industrial applicability: as can be read from the example, the obtained salt is crystallised from isopropanol, but in these conditions a methanesulfonic acid ester is formed, and it is known that these esters are genotoxic and must therefore be eliminated from the final product.
There remains thus a need in the field for a synthesis process of abiraterone or abiraterone acetate of real applicability on an industrial scale.